Buying a condo for investment, when is a good date to purchase house this 1st week of sept?

My birthdate is May 3, 1975 and my husband's Sept. 7, 1970.
I would like to ask your advise as to when is the best date for us to purchase/sign the contract and when should we move in the condo. We plan for the family to use it for about 6 months from time to time but basically for investment for rental.